Refrigeration apparatus



1934- F. J. NATWICK ET AL 7,349

REFRIGERATION APPARATUS Filed Aug. 51. 1928 INVENTORJ "AL 0 W 6 ta 5, QM/1 Patented May 1, 1934 1,957,349 REFRIGERATIONAPPAR'ATUS Frank J. Natwick and Otto G. Tinkey, Pittsburgh, Pa.

ApplicatiohAugu'stBl, 19,28, Serial No, 303,194

'1 Claim. (c1. "ea-126) Our invention relates to refrigerating systems and a method for preventing volatilization of a refrigerant after leaving the heat exchange unit,

and particularly to a heat exchange unit having "'5 provision for preventing the return of liquid refrigerant to a compressor except in a completely volatilized or gaseous form.

n refrigerating systems, it has heretofore been customary to provide a compressor for supplying refrigerant to an expansion chamber through a regulating valve. The expansion chamber is usually in the form of a horizontal cylinder having a number oftubes extending downwardly therefrom and attached at substantially diametrically opposite points on the chamber. The number of such tubes is considerable, and, as each requires two joints for attaching it to the cylinder, considerable difficulty has been experienced in soldering the tubes in place and maintaining the joints leak-proof. With the tubes disposed beneath a horizontally disposed chamber, the natural and rapid circulation of the medium to be cooled is not as great as where the heat exchange unit is in the formof a stack which induces naturalan'd rapid circulation by reason of the change in density of the medium traversing it during the heat exchange operation. v

The expansion chambers of the prior art contain a float'valve that regulates the height of a refrigerant in the chamberand in the connected tubes. By reason of the fact that lubricating oil becomes intermixed with the refrigerant while traversing'the compressor, 'a film of oil floats on the 'top of the liquid refrigerant in the expansion chamber. The presence of this film of oil interferes with the volatilization of the refrigerant, as the volatilized refrigerant must pass through the oil film, which is usually done by the formation of bubbles of sufficient size to displace the oil film.

Furthermore, the tubes discharge volatilized refrigerant gas directly into a comparatively small expansion chamber after the ,gas has passed r through a rather thick oil film. At the same time the circulation of liquid through the tubes at the opposite sides of the chamber creates 'a circulating current which serves to agitate the refrigerant. Each of these agencies serves to agitate the liquid refrigerant in the expansion chamber, and the turbulent condition produces a state of foaming and an emulsion, consisting of gas, oil and liquid refrigerant. No opportunity is given the emulsion to condense or settle its component parts before the volatilized refrigerant is drawn into a suction orifice which leads to the compressor. Another orifice carries off the oil film.

'-By reason of the turbulent condition, the mixtureentering the orifices is neither a completely volatilized refrigerant nor oil. A certain amount of'unvolatilized' refrigerant is carried into each orifice, which results in the volatilizing of the refrigerant in the pipes leading away from the expansion chamber. This action produces a condition usually termed frosting back, in the 'suction lines. In some cases, the unvolatilized refrigerant' has been sufliciently great to enter the compressor -and injure it.

We provide a refrigerating system in which a heat exchange unit, preferably in the form'of a stack, is placed contact with a medium to be cooled, either a'gas'or a liquid. As the heat exchange unit is placed with its axis extending in a vertical direction, the rate of circulation of the medium being cooled is increased by reason of the natural laws governing the movement of a column of fluid having different temperatures at different points therealong.

As the medium becomes cooled, it.'settles toward the bottom'of the heat exchange unit, and as the length of the heat exchange unit is appreciable, the change in temperature and density of the fluid therein is such as to induce considerable draft, This increased draft in turn increases the volatiliz'ation of the refrigerating fluid traversing the cooling unit, with a result that the chiciency' of the refrigerating system is increased. Stated in another way, this action produces a greater amount'of heat radiation per surface unit of the heat exchange unit. The movement of the medium being cooled through the heat exchange unit is'acc'ompanied by a condition of turbulent flow whichbrings more of the medium into direct engagement with the surfaces of the heat exchange unit, than occurs where conduction is relied'upon for cooling the greater part of the medium.

The level of the liquid refrigerant in the system is held constant by a regulating valve. The liquid level is suffici'ently below the top of the heat exchange unit so that ample evaporating space is provided above the liquid level. The volatilized gas gathers in this space, and the regulating valve chamber and heat exchange unit are so designed that the-gas must traverse a conduit permitting the complete evaporation of the refrigerant and the settling of the oil before the gas reaches the intakes of the compressor and the oil drain.

, The regulating valve chamber is preferably made free from tubes or fins which might result llO in the creation of a turbulent condition, such as change units 2 and 4 may be interconnected has heretofore existed where the regulating valve or expansion chamber are provided with heat exchange devices for increasing their radiating surfaces.

The accompanying drawing illustrates certain present preferred embodiments of the invention in which;

Figure 1 is an elevational View of a refrigerating system embodying our invention,

Figure 2 is a plan view thereof,

Figure 3 is an end view thereof,

Figure 4 is a sectional view taken along the section line IVIV of Figure 2,

Figure 5 is a sectional View taken along the section line V-V of Figure 2, and

Figure 6 is a broken elevational view of a modified form of the invention.

Referring to Figures 1 to 3, inclusive, a refrigerating system comprises a plurality of interconnected heat exchange units 2 and 4 and a valve chamber 5 in which a float valve 6 is disposed for controlling the level of a liquid refrigerant in the several heat exchange units and in the valve chamber. The valve chamber is directly attached to the heat exchange unit 2. The heat exchange unit 2 is connected to the adjacent heat exchange unit 4 by a return conduit 7 of relatively large diameter and a smaller pipe 8 through which liquid refrigerant passes. The first heat exchange unit 4 is conected to the second heat exchange unit 4 by a similar conduit 7 and pipe 8.

Liquid refrigerant is supplied to the chamber 5 and the valve 6 by a conduit 9 connected to a compressor not shown. Volatilized refrigerant is withdrawn from the valve chamber 5 through a conduit 10 that also leads to the compressor. As the refrigerant, while traversing the compressor, absorbs and is intermingled with a quantity of oil which floats as a film 11 on top of the liquid refrigerant 12, we provide a drainage spout 14 for the oil. The level of the refrigerant 12 is maintained by the valve 6 to insure that only oil drains through the spout 14. If desired, the drainage spout 14 may be enclosed in the conduit 10.

Referring to Figure 4, the heat exchange unit 2 is constituted by an inner metallic shell 15 and an outer metallic shell 16. The shells 15 and 16 are spaced apart by inserts 17 inserted between the shells 15 and 16 and secured thereto, either by a soldered or welded seam. Feet 18 are attached to the outer shell 16 for supporting the heat exchange unit with its axis in a vertical direction. The chamber 5 is provided with a curved end portion 19 that is attached by a liquid-tight joint to the outer surface of the shell 16. The shell 16 is provided with a plurality of perforations 20 for permitting the movement of the refrigerant 12 and the volatilized gas through it.

The pipe 8 is threaded into the shell .16 and the conduit '7 is secured thereto by a liquid tight joint. Perforations 21 are provided in the shell 16 for permitting the movement of liquid refrigerant and gas through the conduit. The perforated portions of the shell 16 opposite the conduit '7 and the valve chamber 5 serve as baffles to break up and separate unvolatilized or unvolatilizable particles held in suspension by the volatilized gas moving toward the conduit 10.

Referring to Figure 5, the heat exchange units 4 are similar to the heat exchange unit 2, except that conduits 7 and pipes 8 are brought in at different points in the circumference thereof. It is to be understood that the several heat exin shapes other than a straight line, and the number of the units may be varied as desired. The inner surfaces of the shells 15 are provided with fins 22 and braces 24 which serve to increase the radiating surfaces of the heat exchange units.

As the heat exchange units are mounted in a vertical position, the medium to be cooled moves downwardly through the shells 15 in accordance with the well-known laws governing changes in density. The medium to be cooled may be either a liquid or a gas. The downward movement of the medium to be cooled is accompanied by a condition of turbulent flow which brings it directly into engagement with the shell 15, the fins 22 and the braces 24, thereby increasing the eificiency of the heat exchange unit by directly chilling the medium to be cooled rather than by relying upon conduction for cooling a portion of it.

The level of the refrigerant 12 and oil film 11 is maintained slightly above the lower surfaces of the conduits 7. This level is materially below the tops of spaces defined between the shells 15 and 16 and the upper inserts 17. Accordingly, as the liquid refrigerant in the several heat exchange units is volatilized it bubbles upwardly through the oil film l1 and occupies the space in the upper end of each heat exchange unit. The gases in the spaces contain globules of unvolatilized refrigerant and globules of unvolatilizable oil which form an emulsion. If the gases are led directly from such a chamber to the outlet 10 of the compressor they carry with them a certain amount of the unvolatilized refrigerant and the unvolatilizable oil.

The presence of the unvolatilized refrigerant in the pipes leading to a compressor and in the compressor itself causes the volatilization of the gases traversing the pipes and the compressor, which is termed ffrosting back. In some cases a sufficient amount of the emulsion has been carried over into the compressor to form a liquid head, with the resulting destruction of the compressor.

By reason of the perforations in the shells 16, the gases moving toward the outlet 10 are strained before leaving each heat exchange unit. After leaving the heat exchange unit they enter the conduits '7 or the chamber 5, which are relatively quiet as they are generally not subjected to the agitation attendant upon the active chilling of a medium. The chamber 5 is free from tubes which might agitate the refrigerant therein as has heretofore been the case. The gases traversing the conduit 7 and the chamber 5 pass through a relatively quiet zone in which the volatilizable refrigerant is given an opportunity to become volatilized and the oil is given an opportunity to settle out. Preferably, the conduits 7 are made of considerable length in order to secure a complete separation of liquid globules from the volatilized gases. Accordingly, the gas leaving the chamber 5 by the conduit 10 is substantially a pure gas. The pure gas traverses the piping and compressor with which such systems are provided, without frosting back or danger to the compressor.

The amount of refrigerant admitted by the valve 6 varies with the rate of volatilization in the several heat exchange units, but the liquid level is kept constant.

As shown in Figure 6, our invention may be practiced with the heat exchange unit in substantially a horizontal position. In this case, openings 25 and 26 are made through the insert 17 at one end of the heat exchange unit. A valve chamber 2'7 is connected to the openings 25 and 26. The liquid level is maintained low enough to provide a settling chamber above the liquid level. Conduits 28 and 29 are provided for conducting the medium to be cooled downwardly and axially of the heat exchange units as shown by the broken line 30. This form of the invention is otherwise similar to that shown in Figures 1 to 5, and operates in a similar manner.

While We have illustrated and described the preferred form of our invention, it is to be understood that it may be otherwise embodied and practiced within the scope of the following claim.

We claim:

Refrigerating apparatus, comprising an annular double-walled heat exchanger the axis of which is substantially vertical and between the respective walls of which refrigerant is adapted to circulate, a cooled medium being adapted to pass generally axially through the heat exchanger, a compressor, a refrigerant outlet from the heat exchanger to the compressor connected with the heat exchanger near its top but somewhat spaced therefrom, and a refrigerant inlet connected with the heat exchanger near its top and positioned so as to admit refrigerant into the heat exchanger in a direction substantially normal to the inner wall thereof so that the direction of such refrigerant is abruptly changed as it enters the heat exchanger.

FRANK J. NATWICK. OTTO G. TINKEY. 

